The optimal timing of radiotherapy in the combined modality therapy for limited-stage extranodal NK/T cell lymphoma (ENKTL): a systematic review and meta-analysis.

The optimal timing and sequencing of radiotherapy (RT) and chemotherapy (CT) in the treatment of limited-stage extranodal NK/T cell lymphoma (LS-ENKTL) has not been elucidated. The aim of this meta-analysis was to evaluate whether the timing of RT in relation to CT affects the survival of patients with LS-ENKTL. We searched Medline, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science, Clinicaltrials.gov , and relevant meeting abstract databases from inception through April 2018 without age or language restrictions. Studies comparing upfront RT plus CT with induction CT followed by RT in patients with LS-ENTKL were eligible for inclusion. Seven studies with 1593 patients were included, and all were retrospective cohort studies. Compared with induction CT followed by RT, upfront RT significantly improved OS of patients with LS-ENTKL (HR = 0.70, 95%CI 0.55-0.88, P = 0.002), with no evidence of heterogeneity across studies (I2  = 0%). In subgroup analyses, the beneficial effect of upfront RT on survival did not differ significantly between subgroups of studies with different types of chemotherapy regimens (anthracycline-based or non-anthracycline-based), the administration of concurrent chemoradiotherapy or not, and different median doses of RT (≥ 45 or < 45 Gy). These results suggest that upfront RT plus CT confers survival advantage over induction CT followed by RT for the treatment of LS-ENTKL, and this survival advantage is not significantly affected by the types of CT regimens or timing of CT. Given the retrospective nature of included studies, these results should be interpreted with caution in clinical practice.